(1) Field of the Invention
This invention relates to bipolar electrodes and method of manufacturing same, and more particularly to an improved process for manufacturing bipolar electrodes and bipolar electrodes produced thereby.
(2) Description of the Prior Art
A bipolar electrode for electrochemical cells or batteries are plate-like structures having two different electrochemical active materials on opposite surfaces. Electrodes of such type included an active electronegative base metal e.g. zinc, magnesium or aluminum in an electrolyte and an electropositive active material. Such electrodes have been made by coating a sheet of the base metal with an adhesive layer containing the active material of opposite polarity distributed therethrough in finely comminuted form. The adhering polymeric matrix must be sufficiently conductive to form a low-resistance internal current path between the active base plate surface and the other electropositive active material.
The polymeric substance must be resistant to acidic electrolytes, such as chromic or sufuric acid, and is exemplified by ethylene/vinylacetate copolymers (referred to hereinafter as E/VA) which is eminently suitable as a carrier and binder for finely comminuted metallic or carbonaceous particles serving as an electropositive active material. E/VA however, lack the necessary degree of adhesiveness, resulting in its blending with one another resinous substance, more specifically a polymer or copolymer of isobutylene (butyl rubber), with the resulting film incorporating both carbon black and graphite, applied under heat and pressure to the supporting metal sheet.
In U.S. Pat. No. 3,565,694 to Chireau, the process was refined to successive coatings applied under specific conditions. Bipolar support intercell connectors have evolved to complex film material etched to produce craters for depositing active materials, such as described in U.S. Pat. No. 4,091,184 to Erisman to the use of high compressive forces to provide electrical conductivity between the active layers through the conductive separator plates.
While bipolar electrodes of the prior art function in the electrochemical cells, construction of such bipolar plates result in non-uniformity, component separation, or may require mechanical intercell contact.